Guess you've tried every desktop mail client?
I only use one computer and my local mail app (macOS's in my case) just works. I can't imagine trading it for visiting some web site to read my email.
Good for you. I've tried a few during the last 30 years and once Web UIs started being usable (after gmail), I use them if possible.
macOS mail app is a special type of terrible especially if you deal with multiple email accounts. Every os upgrade causes various bugs such as search index all of the sudden not working and you have to reset and reimport all your mailboxes